A nano two-wheeler

According to New Scientist, French and German researchers have built a nanoscale machine with two wheels of a diameter of 0.8 nanometers joined by an axle of only four carbon atoms long. It has been done before, but this time, the nanoscientists have been able to really watch these nano-wheels rolling and rotating over a flat surface. It has been claimed before, but it is the first time that researchers have directly seen this nanowheel rotation. And this discovery probably opens the way to future molecular machines.

According to New Scientist, French and German researchers have built a nanoscale machine with two wheels of a diameter of 0.8 nanometers joined by an axle of only four carbon atoms long. It has been done before, but this time, the nanoscientists have been able to really watch these nano-wheels rolling and rotating over a flat surface. It has been claimed before, but it is the first time that researchers have directly seen this nanowheel rotation. And this discovery probably opens the way to future molecular machines.

This research has partially been done by Leonhard Grill's research group at the Free University of Berlin in Germany. Here are some short excerpts from the New Scientist article.

The researchers created a carbon molecule resembling a pair of wheels just 0.8 nanometres in diameter, joined together by an axle only four carbon atoms long. The achievement was a combined effort by researchers at the Free University of Berlin in Germany (FUB) and the Center for Material Elaboration & Structural Studies (CEMES) in Toulouse, France.

After being chemically synthesised in the lab, hundreds of these "nanowheels" were sprayed onto a sheet of copper. The researchers then used the tip of a scanning tunnelling electron microscope (STEM) to push individual molecules across a copper surface.

Below is a diagram showing how these molecules with two wheels (0.8 nm in diameter) are rolling. You can see how the manipulation using an STM tip can induced a rolling motion (arrows indicate the rotation of the wheels). (Credit: FUB/CEMES)

And below is an illustration showing a calculated molecular configuration of this nano two-wheeler. (Credit: FUB/CEMES)

In a very brief article, "Reinventing the wheel," Nature provides some additional details (scroll to the middle of this PDF page).

Leonhard Grill of the Free University of Berlin, Germany, and his colleagues show that triptycene groups, which resemble three-bladed paddlewheels, can act as wheels only 8 angstroms wide. They fixed one triptycene to each end of a rigid axle, then pushed this primitive molecular vehicle over a copper surface using the tip of a scanning tunnelling microscope.

Evidence that the wheels could 'roll' came from looking closely at how the vehicle moved. When one of its three-armed wheels rotated by 120°, the molecule jumped and its axle reoriented. Nanowheel rotation has been claimed before, but never shown directly.

This research work has been published by Nature Nanotechnology under the name "Rolling a single molecular wheel at the atomic scale" as an advanced online publication (January 21, 2007). Here is a link to the abstract and another one to the full paper (PDF format, 4 pages, 555 KB). This research paper is deeply buried inside Leonhard Grill's publications. However, the above images have been extracted from this letter to Nature Nanotechnology.

Finally, you also should read the a press release from the Centre for Material Development and Structural Studies in Toulouse (CEMES-CNRS), "Turning an axel mounted molecular wheel," which gives some additional details about these future molecular machines.

Sources: Tom Simonite, New Scientist, January 22, 2007; and various other websites

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